We already have a generic PCI_DEVFN() macro in "hw/pci/pci.h"
to pack the PCI slot/function identifiers, use it.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <20201012124506.3406909-6-philmd@redhat.com>
Reviewed-by: Huacai Chen <chenhuacai@kernel.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20201231224911.1467352-4-f4bug@amsat.org>